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Secret Rabbit Code (aka libsamplerate)
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<A HREF="api_misc.html">Miscellaneous</A><BR>
<A HREF="api_misc.html#ErrorReporting">Error Handling</A><BR>
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Author :<BR>Erik de Castro Lopo
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<H1><B>Full API</B></H1>
<P>
The full API consists of the following functions :
</P>
<PRE>
SRC_STATE* <A HREF="#Init">src_new</A> (int converter_type, int channels, int *error) ;
SRC_STATE* <A HREF="#CleanUp">src_delete</A> (SRC_STATE *state) ;
int <A HREF="#Process">src_process</A> (SRC_STATE *state, SRC_DATA *data) ;
int <A HREF="#Reset">src_reset</A> (SRC_STATE *state) ;
int <A HREF="#SetRatio">src_set_ratio</A> (SRC_STATE *state, double new_ratio) ;
</PRE>
<A NAME="Init"></A>
<H3><BR>Initialisation</H3>
<PRE>
SRC_STATE* src_new (int converter_type, int channels, int *error) ;
</PRE>
<P>
The <B>src_new</B> function returns an anonymous pointer to a sample rate
converter object, src_state.
If an error occurs the function returns a NULL pointer and fills in the
error value pointed to by the <B>error</B> pointer supplied by the caller.
The converter must be one of the supplied converter types documented
<A HREF="api_misc.html#Converters">here</A>.
</P>
<A NAME="CleanUp"></A>
<H3><BR>Cleanup</H3>
<PRE>
SRC_STATE* src_delete (SRC_STATE *state) ;
</PRE>
<P>
The <B>src_delete</B> function frees up all memory allocated for the given sample
rate converter object and returns a NULL pointer.
The caller is responsible for freeing any memory passed to the sample rate converter
via the pointer to the <B>SRC_DATA</B> struct.
</P>
<A NAME="Process"></A>
<H3><BR>Process</H3>
<PRE>
int src_process (SRC_STATE *state, SRC_DATA *data) ;
</PRE>
<P>
The <B>src_process</B> function processes the data provided by the caller
in an <B>SRC_DATA</B> struct using the sample rate converter object specified
by the <B>SRC_STATE</B> pointer.
When operating on streaming data, this function can be called over and over again,
with each new call providing new input data and returning new output data.
</P>
<P>
The <B>SRC_DATA</B> struct passed as the second parameter to the <B>src_process</B>
function has the following fields:
</P>
<PRE>
typedef struct
{ float *data_in, *data_out ;
long input_frames, output_frames ;
long input_frames_used, output_frames_gen ;
int end_of_input ;
double src_ratio ;
} SRC_DATA ;
</PRE>
<P>
The fields of this struct which must be filled in by the caller are:
</P>
<PRE>
data_in : A pointer to the input data samples.
input_frames : The number of frames of data pointed to by data_in.
data_out : A pointer to the output data samples.
output_frames : Maximum number of frames pointer to by data_out.
src_ratio : Equal to output_sample_rate / input_sample_rate.
end_of_input : Equal to 0 if more input data is available and 1
otherwise.
</PRE>
<P>
Note that the data_in and data_out arrays may not overlap. If they do, the
library will return an error code.
</P>
<P>
When the <B>src_process</B> function returns <B>output_frames_gen</B> will be
set to the number of output frames generated and <B>input_frames_used</B> will
be set to the number of input frames consumed to generate the provided number of
output frames.
</P>
<P>
The <B>src_process</B> function returns non-zero if an error occurs.
The non-zero error return value can be decoded into a text string using the function
documented <A HREF="api_misc.html#ErrorReporting">here</A>.
</P>
<A NAME="Reset"></A>
<H3><BR>Reset</H3>
<PRE>
int src_reset (SRC_STATE *state) ;
</PRE>
<P>
The <B>src_reset</B> function resets the internal state of the sample rate
converter object to the same state it had immediately after its creation using
<B>src_new</B>.
This should be called whenever a sample rate converter is to be used on two
separate, unrelated pieces of audio.
</P>
<A NAME="SetRatio"></A>
<H3><BR>Set Ratio</H3>
<PRE>
int src_set_ratio (SRC_STATE *state, double new_ratio) ;
</PRE>
<P>
The <B>src_set_ratio</B> function allows the modification of the conversion
ratio between calls to <B>src_process</B>.
This allows a step response in the conversion ratio.
It returns non-zero on error and the error return value can be decoded into
a text string using the function documented
<A HREF="api_misc.html#ErrorReporting">here</A>.</P>
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